Related Articles

"Regardless of the sentence handed down today, it will never change the fact that our son has lost his life in a cowardly and brutal attack that was perpetrated by juveniles.

"It is us and our family that will live with this life sentence. Nothing will ever take away the pain of losing Quinn, our only child."

Judge Reynolds said the offending was an extremely serious example of its kind because Quinn had been lured to an isolated location and left there severely injured after being outnumbered three to one.

"The three of you were persistent," he said.

"The three of you were unrelenting.

"Your whole focus was to get the money."

The teenagers planned to rob Quinn when they lured him to the Balga bush reserve and - brandishing a broken bottle - assaulted him after he refused to give up his belongings, which included $175 to buy the cannabis.

Quinn was punched, kneed and kicked so hard it left a shoe imprint on his head and caused his attacker to limp.

He was chased down when he tried to run away and was found bleeding, bruised and unconscious. He died in hospital the next day.

His attackers, who were around the same age, were initially charged with grievous bodily harm but that was later upgraded to murder.

They last month pleaded guilty to manslaughter - a plea bargain accepted by the prosecution.

Along with the fourth boy, they also pleaded guilty to aggravated armed robbery.

Judge Reynolds said all the offenders had been initially remorseless, with one lying "big time" to police.

They had all developed remorse during the 11 months they have already served at Banksia Hill Juvenile Detention Centre, but in each case, that was overlaid with regret for the impact on themselves, he said.